KR970009957B1 - Roots type rotary compressor - Google Patents

Abstract

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Description

Root type rotary machine

1 shows a profile of one rotor of a root type pump according to the invention.

FIG. 2 is a diagram schematically showing a cross-sectional structure of a pump employing the rotor shown in FIG.

3 shows the relationship between the pressure angle (a) of the involute flow curve and the ratio (D / d) of the involute type rotor outer diameter (D) to the shaft diameter (d).

4 shows the relationship between the ratio (D / d) of the outer diameter (D) to the shaft diameter (d), the shaft strength ratio (A) and the theoretical displacement coefficient (K) for one revolution.

5 is a cross-sectional view taken along the axis of a rotary shaft for driving a first rotor in a route type pump having a rotor according to the present invention provided in a multistage structure.

6 is a sectional view taken along the line VI-VI of FIG.

7 is a view schematically showing the cross-sectional structure of the rotor in the conventional root type pump.

* Explanation of symbols for main parts of the drawings

2,3,22,23,32,42: Rotor 2a, 3a: Tip

2b, 3b: route part, 2c, 3c: involute curve part

26, 27: rotating shaft 36,37: bearing

39: timing gear 50: inlet

52: outlet

The present invention relates to a root type rotary machine such as a roots type pump for use in a vacuum pump system.

Providing sufficient strength to the rotating shaft to ensure stable operation of rotating machines such as rooted type pumps is of paramount importance in terms of design. However, an excessive increase in the diameter d of the rotary shaft relative to the outer diameter D of the rotor results in a decrease in the theoretical displacement for one revolution. Therefore, it is necessary to select the appropriate shaft diameter d in consideration of the displacement and mechanical strength. Envelopes, involutes and cycloid profiles are commonly known as rotor profiles for rooted pumps. In the case of envelope and cycloid profile, the ratio of rotation shaft diameter (d), ie the outer diameter of rotor (D) (diameter of tip circle) to the shortest diameter (diameter of circle circle), is basically determined. In contrast, in the case of the involute route profile, the ratio D / d can be preferably changed by changing the pressure angle a of the involute route within a certain range.

In FIG. 7, which shows a typical conventional involute type rotor, each tip 12a, 13a is the outer diameter of the rotor across the involute curves 12c, 13c (diameter of the tip circle). In contrast, each root angle 12b, 13b crosses the involute curves 12c, 13c and also contacts a circle of diameter d. r _ο ). The theoretical displacement for one revolution corresponds to six times the trapping space 14 (in the case of a trilobite rotor) defined between the housing 11 and the rotor 12 and is expressed as follows.

V = KD²L

V: theoretical displacement for one revolution

D: Outside diameter of rotor

L: Thickness of the rotor (depth of space occupied by the rotor)

K: theoretical displacement factor

The theoretical displacement factor K is determined by the rotor profile. By maximizing the theoretical displacement coefficient K, the displacement of the pump can be increased.

In the case of the involute type pump having the shape shown by way of example in FIG. 7, the enclosed space 15 is limited to the area of the engagement engagement between the rotor 12 and 13, and this space 15 This results in several drawbacks such as rotor 12, increased power consumption and reduced displacement during the trapping process, resulting in a loss of pump operation. In particular, the prior art has the problem that the enclosed space 15 is increased as the pressure angle a becomes smaller.

In view of the above situation, the main object of the present invention is designed to minimize the enclosed space, which is one of the drawbacks of the conventional involute type rotor, and at the same time to assure the advantages of the involute type rotor within a certain range. A rotary machine of the involute type which can preferably select the ratio (D / d) of the outer diameter (D) of the rotor to the shaft diameter (d) by varying the pressure angle (a) of the involute curve To provide.

To this end, the present invention comprises a housing having a suction inlet and an outlet and at least two rotors jointly configured in one step, the rotor being disposed in the housing and having individual shafts which rotate in opposite directions to each other. In a rotary machine that sends gas toward the head, a circular arc (radius) in which the tip of each rotor is relatively smoothly in contact with the involute curve centered on the rotor's base circle (circle of diameter R shown in FIG. 1). At the same time, the root portion of each rotor is defined by an arc of radius r '(r + gap), which traverses the involute route centered on the base circle, with a substantially constant gap between the rotors. And the ratio (D / d) of the diameter D (the diameter of the tip circle) of each rotor to the diameter d (the diameter of the root circle) is within the range represented by To provide a rotary-type machine that Lou agent being selected.

D/d

[1+sin(180 /2n)]/[1-sin(180 /2n)]

D / d

[1 + sin (180 / 2n)] / [1-sin (180 / 2n)]

3Where n is the number of wings in the rotor: n

3

The apparatus makes it possible to select the shaft diameter d preferably within a range for a given rotor outer diameter D. The optimum shaft diameter d can be selected taking into account the theoretical displacement coefficient (shown in FIG. 4) for shaft strength and one revolution. Therefore, it is possible to make an involute type rotor designed so that there is virtually no sealed space that can cause vibration and noise, increased power consumption, and reduced displacement, and that a substantially constant rotor gap is always ensured.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a profile of one rotor of a root type pump according to the present invention, and FIG. 2 schematically shows a cross-sectional structure of a root type pump employing the rotor shown in FIG. As is clear from the figure, the leading end portions 2a, 3a of the outer diameter D 'are respectively corresponding involute curve portions 2c centered on the base circle (diameter R) of the conventional involute type rotor. ) And (3c) are limited to circular arcs (radius r). Similarly, the root portions 2b and 3b each have a radius r '(r + gap) centered on the base circle and Limited to an arc that crosses the corresponding involute curve, and thus a smaller ratio D '/ than the ratio of the outer diameter D to the shaft diameter d of the conventional involute type rotor. A new involute type rotor having an d ') can be obtained (outer diameter D' (D), shortest diameter d ') (d)).

3 shows the relationship between the ratio D / d of the outer diameter to the shaft diameter of the involute type rotor and the pressure angle a of the involute curve. It is possible from FIG. 3 to obtain the ratio D / d of the outer diameter D to the shaft diameter d at the pressure angle a employed as a parameter. Since the pressure angle a represents the profile of the involute curve, the ratio D / d of the outer diameter D to the shaft diameter d is constant for the predetermined pressure angle a. Thus, if the pressure angles are constant, the profiles of the two rotors each having a different outer diameter D 'relative to the outer diameter D are similar to each other. This means that the rotor profile is determined if the pressure angle a is obtained from the shaft diameter d and diameter D necessary for the rotation shaft of the rotor when the predetermined rotor outer diameter D is constant.

When the rotors 2 and 3 are coupled to each other and sealed in the involute route curves 2c and 3c, a substantially constant gap is maintained as a characteristic of the involute route curve, and the substantially constant gap is a luu. The radius of the circular arc defining the troughs 2b, 3b is set to r 'so that it is always maintained in the region between the leading ends 2a, 3a and the roots 3b, 2b, and r' It is determined by adding a gap to the radius r of the arc defining the tip portions 2a and 3a.

This arrangement enables the minimization of the enclosed space 15, which is one of the drawbacks of the prior art as shown in FIG.

As described above, since the shaft diameter d can be preferably selected within a certain range for the predetermined rotor outer diameter D by employing the pressure angle a of the involute curve as a parameter, As shown in the figure, the optimum shaft diameter d can be selected in consideration of the theoretical displacement coefficient for one revolution and the shaft strength. Furthermore, the optimum shaft diameter (d) is the ratio (D / d) of the outer diameter (D) to the shaft diameter (d) in the case of a cycloidal rotor and the ratio (D / d) in the case of an envelope type rotor. It can be selected within the following range, wherein the two types of rotors having a ratio (D / d) are mainly determined as follows.

D/d

[1+sin(180 /2n)]/[1-sin(180 /2n)](n + 1) / (n-1)

D / d

[1 + sin (180 / 2n)] / [1-sin (180 / 2n)]

3Where n is the number of blades in the rotor: n

3

Moreover, there is no practically enclosed space between the rotors 2 and 3, and a substantially constant rotor clearance is always maintained between them.

5 and 6 show a combination with another embodiment, in which the present invention is employed in a multistage vacuum pump. In this multistage vacuum pump, the air is sucked into the first stage pump consisting of two triple blades 22 and 23 via, for example, the suction port 50 in communication with the vacuum chamber, and then the pressure is lower than the suction port side. It is discharged to a somewhat higher outlet 52.

Air is then directed to the inlet (not shown) of the second stage pump, including the rotor 32, and then discharged to the outlet where the pressure is maintained even higher by the operation of the second stage pump. In this way, the air sucked in from the inlet port 50 passes through a plurality of pumps arranged in series, gradually increasing the air pressure, and the air is discharged from the outlet port of the final stage pump. In this way, the air sucked from the inlet 50 passes through a plurality of pumps arranged in series, gradually increasing the air pressure, and the air is poured into the outlet of the final stage pump and discharged into the atmosphere.

In the embodiment shown in FIG. 5, as long as the rotary shaft 26 is supported by the bearings 36 and 37 which are firmly fixed to the housing 21, the rotary shaft 26 has a first rotor at first to third stages. 22, 32, and 42 are driven. The rotary shaft 26 is driven by the operation of the motor 38 operably connected to one end of the shaft 26.

The rotary shaft 26 is driven by the operation of the timing gear 39 at the other end of the rotary shaft 26. 23) is arranged to rotate simultaneously with the other rotary shaft 27 that drives.

In the multistage pump shown in FIG. 5, the load on each of the rotary shafts 26 and 27 will increase because each shaft drives a plurality of rotors. However, in the present invention, the shaft diameter d is set so that the maximum stress of each rotating shaft is smaller than a predetermined value by employing an involute type rotor and by selecting an appropriate value for the pressure angle of the involute curve. Can be selected, thereby providing a suitable mechanical strength for the rotating shaft. Furthermore, by limiting the tip and the root of the rotor to circular arcs, the enclosed space can be substantially removed, thereby minimizing the generation of vacuum and noise.

Although the trilobal rotor is employed in the above embodiment, the present invention can be applied to any rotor having three or more wings. Grooves or other local regions outside the arc can be formed at the tip of each rotor. In the above embodiment, the present invention is applied to a root type pump, but the present invention can be widely applied to a root type revolving machine such as a root type flow meter in addition to the root type pump.

As described above, the present invention provides the following advantages.

As shown by way of example in FIG. 4 for a given rotor outer diameter D, the optimum shaft diameter d can be selected within a range in consideration of the theoretical displacement coefficient for one revolution and the shaft strength. Therefore, a loop that employs an involute type rotor so that there is substantially no enclosed space that can cause vibration and noise, increased power consumption, and reduced displacement, and that a substantially constant rotor clearance is always ensured. Type pump can be provided.

Claims (2)

A housing having an inlet and outlet and at least two rotors configured in combination at one end, the rotor having individual shafts disposed within the housing and rotating in opposite directions from the inlet to the outlet A root type rotary machine for discharging gas; The respective rotors each have a tip portion and a root portion formed by an arc; The tip portion and the root portion are smoothly connected to each other through an involute route curve; The spacing between the rotors is maintained at a substantially constant level, and the ratio (D / d) of the diameter (outer diameter) D of each rotor tip member to the diameter (shaft diameter) d of the root circle is (n + 1) / (n-1)

D / d

[1 + sin (180 / 2n)] / [1-sin (180 / 2n)] Where n is the number of blades in the rotor and n

Root type rotary machine, characterized in that it is selected to be in the range (3). According to claim 1, wherein each of the two ends of the rotor is fixed to each of the two shafts for rotating the rotor in the opposite direction to each other to form a longitudinal extension in each of the extension, Root type rotary machine, characterized in that each of a pair of rotors constituting the other stage is fixed and rotated.

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